Question

Среди студентов некоторой группы 2/5 юноши и 3/5 девушки. Половина студентов – юношей данной группы моложе 21 года, среди студенток – девушек моложе 21 года – 2/3. Чему равна вероятность того, что случайно выбранный учащийся, возраст которого меньше 21 года, - это девушка.

Answer 1

Ответ:

Мне кажется ответ 40%, т.к юношей моложе 21 г - 1/2 (половина студентов-юношей), а девушек моложе 21 г - 2/3 из числа студенток. Нужно приплюсовать количество студентов (юношей и девушек) моложе 21 г и определить из этого часть девушек моложе 21 г. Ответ будет 2/5 (40%) вероятности того, что случайно выбранный учащийся, возраст которого меньше 21 года, - это девушка.

Решение:

100% : 5 • 2 = 40%

Надеюсь понятно

Answer 2

Given Information:

- Among the students in a certain group, 2/5 are boys and 3/5 are girls. - Half of the students in the group are boys younger than 21 years old. - Among the girls, 2/3 are younger than 21 years old.

Calculating the Probability:

To find the probability that a randomly chosen student, who is younger than 21 years old, is a girl, we need to consider the given information.

Let's assume there are 100 students in the group for simplicity.

- The number of boys in the group would be 2/5 * 100 = 40 boys. - The number of girls in the group would be 3/5 * 100 = 60 girls.

According to the given information: - Half of the students in the group are boys younger than 21 years old. So, the number of boys younger than 21 would be 1/2 * 40 = 20 boys. - Among the girls, 2/3 are younger than 21 years old. So, the number of girls younger than 21 would be 2/3 * 60 = 40 girls.

Therefore, the total number of students younger than 21 years old would be 20 boys + 40 girls = 60 students.

To find the probability that a randomly chosen student, who is younger than 21 years old, is a girl, we divide the number of girls younger than 21 by the total number of students younger than 21:

Probability = Number of girls younger than 21 / Total number of students younger than 21 = 40 girls / 60 students = 2/3.

So, the probability that a randomly chosen student, who is younger than 21 years old, is a girl is 2/3.